FIELD OF THE INVENTION
The invention relates to a device for adjusting the oblique register in a clamping device for locking printing plates in an offset printing machine, in which a clamping bar with means for opening and closing a gap is oriented for insertion of the front or rear edge of a printing plate at the jacket face of the plate cylinder parallel to the cylinder axis, and in which a centering bolt oriented radially to the plate cylinder and extending into the insertion gap is secured, the centering bolt having a profile which corresponds to the profile of a centering groove in the insertion edge of the printing plate.
It is known for printing plates to be clamped in the plate cylinder of an offset printing machine in clamping bars. To obtain a precisely defined position of the printed image on the printed sheet of paper, the printing image located on the printing plate must also be in a very precisely defined position. Various inaccuracies, however, for instance in the area of the make-up of the image on the plate, due to stamping errors in the printing plate or other errors in the preliminary printing stage, including possibly incorrect locking of the printing plate, can lead to repeated occurrences of slight deviations of the printing image on the printing plate from the defined position thereof on the plate cylinder. Particularly in multicolor printing, the printing images mounted on the printing plates must be matched accurately relative to one another. To compensate for these deviations of the printing image from the defined position, it is known to provide correction devices for correcting the position of the printing plate in the plate cylinder. Corrections may become necessary in order to adjust the printing image laterally, circumferentially, and obliquely.
For oblique adjustment, it is known to employ complicated, expensive provisions for final oblique adjustment, relative to the plate cylinder, of the clamping bars for locking the printing plate, after the printing plate has been locked.
The object of the invention is to enable genuine oblique adjustment of the printing plate, simply and economically.
According to the invention, this is attained by the embodiment of a clamping device for locking printing plates in an offset printing machine in accordance with the characteristics of claim 1. The stop, adjustable in the circumferential direction, in the clamping bar enables simple oblique adjustment of the printing plate. The printing plate is centered on one side with a prestamped centering groove in the fixed centering bolt and can be rotated about the centering bolt and thus obliquely adjusted by simple adjustment of the stop, which acts in the clamping bar on the other side of the printing plate. In the case of manual actuation, the clamping bar is first opened, then the stop is adjusted in accordance with the deviation value, which is ascertained in a conventional manner, and once the plate is in place again the clamping bar is closed again. An adjustment even before locking is also possible, if the deviation is ascertained beforehand in a conventional manner from the printing image on the printing plate. Automatic opening, remeasurement, readjustment and closure is also possible in a simple way. The oblique adjustment enables correct adjustment of the position with little effort or expense.
The embodiment according to the invention as defined by the characteristic of claim 2 is especially simple and economical. Additional adjusting means can be dispensed with. A stop as defined by the characteristics of claim 3 is especially easy to use and to make. By simply rotating the stop about its axis of symmetry, reliable oblique adjustment is possible. An embodiment according to the invention as defined by the characteristics of claims 4 and 5 additionally promotes secure, reliable control of the oblique adjustment without major effort or expense. The embodiment as defined by the characteristics of claims 6 and 7 represent especially preferred embodiments. An especially simple economical clamping device is made possible by the embodiments defined by the characteristics of claims 8-10.
The embodiment of the invention in accordance with the characteristics of claim 11 additionally enables easy control with the aid of a tool. This tool can be coupled permanently or releasably with the stop under automatic control.
The embodiment according to the invention as defined by the characteristic of claim 12 additionally promotes the accurate adjustment of the stop and hence the accurate oblique adjustment of the plate.
The embodiment according to the invention as defined by the characteristic of claims 13 and 14 furnishes especially simple, reliable clamping devices for the oblique adjustment.
The invention will be described in detail below in terms of the embodiments shown in FIGS. 1-6.